Acoustical Properties of Materials Chapter 8. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson.

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<ul><li><p>Acoustical Properties of MaterialsChapter 8</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>SoundResponse of human ear to pressure fluctuations in the air caused by vibrating objects. Sound wave is a back &amp; forth vibratory motion passed from particle to particle through a medium Sound frequency is the number of back and forth cycles that occur in one second ( measured as Hertz) Audible frequency range lies between 20 Hz &amp; 20,000 Hz</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Sound wave produced by tapping on wall</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>WavelengthDistance between peaks in a sound wave</p><p>Speed = Frequency X Wavelength</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Sound pressure (loudness) measured on decibel scale</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Types of sound: Airborne sound</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Types of sound: Structure-borne sound (impact sound)</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Airborne sound falling on a building assembly</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Airborne sound &amp; building assemblySound is reflected, absorbed &amp; transmittedTransmission rate varies with weight of assemblyHeavy-weight assemblies are poor transmitters - good insulatorsLight-weight assemblies, poor insulators</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Sound transmission loss (TL): the loss of sound pressure level as sound passes through an assemblyMeasured in decibels (dB)Difference in sound pressure level between the source side and receiver sideThe greater the TL of a wall, the better it is as a sound insulatorTL varies with frequency, generally higher TL with higher frequency sound</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Sound transmission loss</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Sound Transmission Class (STC)Single number index- average of TL over frequencies ranging from 125 Hz to 4 kHz</p><p>Used to compare building assemblies</p><p>Regulated by code in some building types</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Decibel scale</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Improve STC of light weight assemblies byAdding fibrous insulation in stud cavities</p><p>Decoupling gypsum board layer</p><p>Use multiple gypsum board layers</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Stud wall assemblies</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Resilient Channel</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Resilient Clip</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Impact Insulation Class (IIC)measure of structure-borne sound</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Sound absorptionSound originating within room attenuated only through sound absorptionNoise reduction coefficient used to compare efficacy of materials (0-1)Higher NRC, the more sound absorptive the materialMaterials .2 NRC or higher are sound absorptive</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Ceiling tiles</p><p>Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved.</p><p>Partitions: fabric-wrapped fiberglass panels absorb sound</p></li></ul>

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